There's been an almost visceral reaction to how rapidly and sharply the show's quality has dipped, and just how much promise Smash has thwarted. It's stumbled, "face first, into the orchestra pit," says Jace Lacob at The Daily Beast. And he's right: The characters have become one-dimensional caricatures whose motives are confounding, when they exist at all. Monologues accompanied by piano tinkles at the end of Full House are less corny and more believable than the show's dialogue. Critics are marveling at the lack of acting talent displayed by the young man playing Debra Messing' son. A recent episode featured characters performing a fully choreographed rendition of "Dance to the Music" at a bowling alley while Meryl Streep's daughter tornadoes through, sprinkling Peace Corps fairy dust over everyone's problems before becoming so stressed by their ridiculous machinations that she announces she must flee to "count wild salmon in Alaska." In other words: It's bad.

So, a musical TV show debuts to standing ovations, praised for its ambition and bravery in daring to merge the worlds of theater and television—only to soar off the rails in such grand a fashion that even its biggest supporters can't help but shake their heads in dismay. Sound familiar? It's exactly the plight of Glee, the cheeky song-and-dance soap opera whose initial success arguably paved the way for Smash. What started as a candy-colored breath of smart-and-snarky air quickly became muddled by overly earnest "message" episodes, laughable dialogue, a glut of unlikable characters, and jarring tonal shifts. Currently, both shows are at a crossroads: Smash recently received a second-season renewal, but fired the showrunner responsible for its cacophonous premiere season. Glee returns after an extended hiatus Tuesday night to close out a season that will see a crop of pivotal characters graduating high school—and perhaps the show. Some might view these as opportunities to regroup, restructure, and reboot. But perhaps a better idea would be to face the music: The TV musical experiment has failed.

Back in 2009 when Glee premiered, there were legitimate doubts that the show would ever catch on. The musical TV show graveyard is littered with series that failed to bring musical storytelling to the tube. Cop Rock and Viva Laughlin couldn't make it work. Neither could Fame, which, despite its cult status, received ratings so low that it was canceled after two seasons—living on only thanks to a syndication deal. Glee initially was a ratings smash, getting as many as 13 million viewers for episodes in its first season. Those days are long gone. Ratings for season three have been in free fall, hitting series lows. Smash has followed a similar trajectory, debuting to a stellar-for-NBC/mediocre-for-any-other-network 11.5 million viewers, then falling to almost half that number for its most recent episode. For both series, ratings have slipped as dramatically as the quality. That viewer interest in musical TV shows is waning couldn't be more obvious if Ryan Murphy wrote a "very special episode" of Glee about it.

Further signs that this so-called musical TV show revival has hit a bum note: At one point after Glee premiered as a bona fide hit, almost every major network was developing a musical pilot. It's telling, however, that besides Smash, none of them made it to air. The splashiest one, Miraculous Year—directed by Kathryn Bigelow and starring Frank Langella, Hope Davis, Susan Sarandon, and Patti LuPone—even produced a pilot that HBO decided to pass on. Without actually being in the executive's office, it's hard to say why these projects were killed. But given the inconsistency and quality-control problems plaguing Smash and Glee, it's not hard to imagine that they struggled to achieve the tricky balance between realism and razzle-dazzle those shows need to work. That doesn't bode well for two more dubious-sounding musical TV shows in development for the fall—a Country Strong rip-off titled Nashville and the time-travel musical romance (for real) Joey Dakota.

It may seem strange that movie musical is once again flourishing while it's taken 70-plus years for the TV musical to finally have a moment—a moment that's quickly slipping away. Since 2002's Chicago triumph, the movie musical renaissance may have suffered as many misses (Nine) as hits (Hairspray), but Hollywood's now-decade-long reliance on the genre shows no sign of ceasing, with big-budget, splashy adaptations of Rock of Ages and Les Miserables in the pipeline. But movies have a distinct advantage over television musicals: Movies get to stuff beginnings, middles, ends, and rousing showstoppers into tidy, self-contained 90-minute packages. Glee produces 26 one-hour episodes per year, and it's proven excruciatingly difficult to tell stories through song serially at that pace. A musical with just one sequel is rare—let alone 25 each year. Or perhaps it's the "event" status of musicals on Broadway or the big screen that make them such reliable successes. Not many people feel the need to schedule dates with their friends because Rachel and Finn are singing yet another '80s pop song in the McKinley High choir room. Either way, something's not gelling when Mamma Mia! rakes $600 million at the global box office but an episode of Rob trumps Smash in the ratings.

Glee and Smash both gave it the old college try, producing undeniably fantastic moments of television along the way—historic moments, even, in the case of Glee. But every good theater performer knows when it's time to take a graceful bow and exit the stage. Let's draw the curtain on the TV musical.